A.positive head
B.negative suction head
C.mechanical seal
D.vent valve attached to the casing at the top of the volute
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A.gate valve
B.globe valve
C.check valve
D.plug cock
A.At the designed operating temperature, the liquid refrigerant charge has changed to a vapor
B.The liquid refrigerant tends to collect at the bellows or diaphragm and reduces the valve sensitivity
C.The sensing bulb is empty of liquid refrigerant charge at the designed operating temperature
D.The sensing bulb is never emptied of liquid refrigerant under normal operating conditions
A.diaphragm type gage
B.pressure transducer
C.manometer
D.All of the above
A.reduce radial thrust to the impeller
B.double the liquid velocity through the pump when compared to a single volute
C.reduce hydraulic end thrust
D.provide the effect of multi-staging
A.dirt will cause corrosion of bearing
B.bearings will leak oil excessively
C.dirt is very abrasive when mixed with grease
D.grease will become inflammable
最新試題
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
Thermostatic expansion valves can be adjusted for （）.
The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its （）.
The general purpose of a heat exchanger is to （）.
Who is responsible for ensuring that someone is assigned to close the watertight doors in an emergency?（）
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.
If the thermal bulb of an expansion valve is incorrectly placed at the center of the coil instead of the end, it will （）.